Vacuum condenser



Nov. 20, 1945. E. J. MURPHY VACUUM CONDENSER Filed Aug. 25, 1943 /N V/vo/e EJ. MURPHY Afro/wey ffl-[TIT Patented Nov. 20, 1945 vAcUUM coNnENsEa Edward J. Murphy, Summit, N. J., aasignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation oi New York Application August 25, 1943, Serial No. 499,895

2 Claims.

This invention relates to electrical condensers and more particularly to vacuum condensers..

According to the present invention. the lives of unimpregnated electrical condensers having solid dielectric spacers, particularly those having celluloslc spacers. are considerably increased and the dielectric strength of the dielectric is increased by maintaining the condenser under a. high vacuum during use. This high vacuum is maintained within the envelope in which the condenser is sealed by the inclusion of a small amount of a highly adsorbent or absorbent solid which absorbs any gases evolved by the action of heat or electric potential upon the solid dielectric.

One manner in which the invention may be practiced is shown by way of illustration in the accompanying drawing in which:

Fig. 1 is a perspective view, partly in section, of a vacuum condenser of the present invention; and

Fig. 2 is a front elevation, in section, of the same condenser.

Referring to Figs. 1 and 2, the condenser unit is of the conventional rolled foil type made up of two metal foil electrodes 2 interleaved with spacers or' condenser paper 3, the whole being rolled into a compact unit. Metal strips 4, 4 and 5, 5 are connected respectively to the two foil electrodes in the conventional manner and serve as leads for the electrodes. 'Ihe condenser unit is supported by the metallic supports S and 1 to 'which are soldered the leads 4, 4 and 5, 5. 'I'he metallic supports 6 and 1 are joinedat the top by a bridge l of insulating material, to which they are fastened in any suitable manner. The supports 6 and 1 are in turn supported by the metal Wires or rods 9, I0, II and I2 to which they are connected electrically. These wires or rods are imbedded in and supported by the glass stem I3. The entire unit is enclosed in a sealed and evacuated glass envelope I4. The glass envelope is mounted on a suitable base I5 which is provided with dummy prongs I8 and I l and terminal prongs I8 and I9. Lead wires 20 and 2I connect the terminal prongs Il and I9, respectively, with the support wires 9 and I2, respectively. A container 22 for solid gas sorbent is supported within the envelope in any suitable manner. This container is open at one end and is provided with'a porous cover 23 at this endrfor permitting the entry oi.' gases while preventing the escape of the solid sorbent.

The electrical device described above may be prepared using conventional rolled foil condenser technique and conventional vacuum tube technique. Any suitable condenser paper such as linen, cotton, or kraft paper may be used. In Place of paper, any sheet cellulosic material of the requisite thinness, such as sheets of regenerated cellulose or of cellulose derivatives, such as cellulose acetate, may be employed. Thin textile fabrics may also be used, such as thin cotton gauze and in particular the highly purified cotton gauze of the type used for bandage pur- 4 Although the degree of evacuation necessary will vary somewhat with the spacing of the electrodes and the voltage to which the condenser is subjected, it is ordinarily necessary that a vaeuum of the order of not more than 10-2 milli-4 and hydrogen. Ii these gases are not removed,

it has been found that, after a period of operaation, the pressure within the evacuated envelope rises to a point where the beneficial effects of high evacuation are no longer obtained. It has also been found that by placing suitable solid sorbent materials within the evacuated envelope, the required degree of evacuation can be maintained for considerable periods of time.

It has been found that a nely divided mixture of three parts of activated alumina or magneslum perchlorate, two parts of soda lime, and one part of hopcalite, form a very effective sorbent for the purposes of the present invention. Hopcalite is a mixture of about 5o per cent manganese dioxide, 30 per cent cupric oxide, 15 per cent cobalt oxide and 5 per cent silver oxide. The hopcalite serves as a catalyst for the oxidation of carbon monoxide to carbon dioxide, which in turn, together with any other carbon dioxide present, is absorbed by the soda lime. The activated alumina and magnesium perchlorate serve to absorb any water vapor present. Obviously any other suitable solid sorbent materials having slmilar properties may be used in place of these substances. For condensers having capacities up to about one microfarad, between about one gram and about five grams of sorbent material is sufllcient.

Although the invention has been described in terms of its specinc embodiments, certain modincations and equivalents will be apparent to those l skilled in. the art and are intended to be included within the ,scope of the invention, which is to be limited only by the fmt-.w scope of the are in an evacuated envelope, said celiulcsiel 5.1.1.

said condenser ,1u-.s the normal oationof evol g which fr/end'to reduce'the vacuum ind enveicpe, said gases sir carbon 1.5 v @www monoxide, said envelope 'erwis- 2,389,207 'bent material for sorbing said gases from thev Space f-l said condenser, said sorbent material includin means for oxidizing carbon monoxide to carbon' dioxide.

2. An electrical device comprising anv electric condenser, the dielectric of which comprises a cellulosic material, said condenser being enclosed in an evacuated envelope, said cellulosic material d the normal operation of ysaid condenser evolving gaseswhich tend to reduce the vacuum, and a solid sorbent material forsorbing gases evolved from the cellulosic dielectric during the operation of the condenser, said sorbent'l material comprising nely divided soda lime, actiand hopcalite.

' @WARD J. MURPHY. 

